So it's a Gatwick departure on one of the G-GATx series aircraft by the look of it - many people love 2D/F on those aircraft for the great legroom, so it's not a surprise to see those gone. Those variants don't have the wardrobe in front of 1A/C, so those seats are open and facing the crew jumpseats, which some people don't like, and they would be restricted to Gold anyway if the flight is more than 72ish hours away.

As I say, if it's very recent that you moved to Silver (and the flight is not in the immediate future) there's a very good chance it will resolve itself over the coming days and you can select online for free.

Perhaps the agent was getting confused because seeing 2D/F being against a bulkhead they thought that bulkhead rows were reserved for Golds? But it's just Row 1 on shorthaul that is reserved in that way. In most of the fleet, the bulkhead will be Row 1 so that's perhaps understandable, but these variants are, as you can see, a bit different.